Insulated metal panels (IMPs) are often used as roofing panels, wall panels and the like. In an IMP has thin gauge metal panels with a layer of insulation between the metal panels. The insulation layer is typically about two to six inches in thickness, but can be of any thickness.
In a typical roofing IMP installation, the panel (which is prefabricated), is laid on the underlying structure, for example, the steel deck of a roof. A membrane may be positioned over the panel and self-drilling screws are then driven through the membrane, the top panel, insulation and bottom metal panel into to the underlying substrate. Alternately, a washer, such as a resilient (e.g., rubber) washer is placed on the fastener or outer surface of the panel, and the fastener is driven through the washer and the panel and into the substrate. The membrane or washer provide a weather resistant seal between the fastener and the panel.
One drawback to the use of such fasteners is that metal debris or shavings from the IMP can be generated that can have a negative impact on the integrity of the membrane or washer. That is, as the threads penetrate the outer panel, insulation, inner panel and substrate, debris, such as shavings or cuttings can be pulled up by the threads as the fastener is driven into the panel. The debris, some of which is metal shavings, can become lodged between the head of the fastener and the membrane or washer. Because the nature of the shavings is such that there are sharp edges and points, the shavings can cut or puncture the membrane or washer, thus compromising the integrity of the membrane or washer and impacting the ability to maintain weather resistance.
Another drawback to the use of such fasteners is that the fastener thread may pull up the top panel when the point penetrates the substrate. This can detach the top panel from the insulation layer. Moreover, such fasteners can be easily over-driven, thus reducing the IMP thickness and impacting the insulating ability of the IMP.
Accordingly there is a need for an improved fastener that is self-drilling and self-cleaning. Desirably, such a fastener reduces the likelihood of damage to the panel and to any weather-resistant member associated with the panel, during installation. Desirably, such a fastener securely fastens an IMP to a secondary structure and does not compromise the integrity or efficiency of the panel.